The present disclosure relates to an image processing apparatus and method and in particular relates to an image processing apparatus and method that are capable of suppressing an increase in the processing load while realizing a significant reduction in data size.
In recent years, it has become increasingly common for digital still cameras and the like to include, as a mode for storing image data, a RAW compression mode in addition to a JPEG encoding mode where image data is encoded according to JPEG (Joint Photographic Experts Group) standard.
When JPEG encoding mode is used, developing processing, such as demosiacing, is carried out on pixels of the color components read from an image pickup element, pixel interpolation is also performed, and then the data is encoded according to JPEG standard. Since JPEG is an irreversible encoding method, when this mode is used, the original image information is lost.
Conversely, when a RAW compression mode is used, the data size is reduced by carrying out image processing on the pixels of the color components read from an image pickup element. Accordingly, in many cases this mode uses reversible compression. Also, since intermediate processing such as demosaicing and pixel interpolation is unnecessary, there is little computational load and because interpolation is yet to be carried out, it is possible to carry out processing on an image that still has a low resolution (i.e., small size).
It is therefore possible to maintain the image quality of the image pickup element. For this reason, RAW compression is becoming increasingly necessary as a format capable of compression and storage with no loss in the pixels of the color components.
As one example of a RAW image compression method, a method that carries out a specified color transform on the four color components (R, G0, G1, B) of a Bayer pattern to transform such components to the four components Y, Cb, Cr, and Cg has been proposed (see for example, Japanese Patent No. 4,436,733).
A method that uses a Karhunen-Loeve Transform (hereinafter “KLT”) for such a color transform process has also been proposed (see, for example, “Analytical Evaluation on the Energy Compaction Provided by Karhunen-Loeve Transform” by Ohbayashi Hiroki, Bandoh Yukihiro, Takamura Seishi, Jozawa Hirohisa, and Yashima Yoshiyuki in “1E10E Transactions on Fundamentals” submitted on Vol. J93-A No. 9 pp. 636-637, 2009.12.7 and resubmitted on 2010.5.10).